THE MEDIUM RANGE MODELS BEGIN THE DAY 4 TO 8 PERIOD WITH ZONAL FLOW ACROSS THE CONUS ON SUNDAY AND SUNDAY NIGHT/DAY 4. ON MONDAY/DAY 5...AN UPPER-LEVEL TROUGH DEVELOPS IN THE SWRN STATES WITH THIS FEATURE MOVING INTO THE ROCKIES MONDAY NIGHT. THE MODELS ARE NOW IN VERY GOOD AGREEMENT...MOVING THE SYSTEM INTO THE HIGH PLAINS ON TUESDAY WITH MOISTURE RETURN TAKING PLACE ACROSS THE SRN PLAINS DUE TO A WELL-DEVELOPED LOW-LEVEL JET. STRONG THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE FROM TUESDAY AFTERNOON/DAY 6 THROUGH TUESDAY NIGHT ON THE WRN AND NRN EDGE OF THE MOIST AXIS FROM THE SRN PLAINS AND OZARKS NEWD ACROSS THE MID-MS AND OH VALLEYS. ON WEDNESDAY/DAY 7...THE ECMWF AND GFS DIVERGE SHARPLY WITH THE GFS MOVING A COMPACT SYSTEM ACROSS THE CNTRL ROCKIES AND THE ECMWF DEVELOPING A BROAD UPPER-LEVEL TROUGH IN THE WRN STATES. DO TO THESE LARGE DIFFERENCES...CONFIDENCE IS VERY LOW LATE IN THE DAY 4 TO 8 PERIOD. AT THIS POINT...TUESDAY AND TUESDAY NIGHT HAVE THE GREATEST POTENTIAL FOR SEVERE WEATHER BUT WILL NOT OUTLOOK AN AREA DUE TO UNCERTAINTIES OF MAGNITUDE AND TIMING CONCERNING THE UPPER-LEVEL SYSTEM.

...DISCUSSION... PER 00Z ECMWF/GEFS GUIDANCE...AN INITIALLY ZONAL WEST-EAST UPPER FLOW REGIME TO BEGIN THE PERIOD WILL QUICKLY AMPLIFY TO A DEGREE WITH SHORTWAVE FEATURES EMBEDDED WITHIN LOW AMPLITUDE WEST-SOUTHWESTERLY FLOW ALOFT THROUGH MID/LATE WEEK. THAT SAID...A MODEST PREDICTABILITY REGIME EXISTS /ESPECIALLY BY DAY 6-8/ OWING TO THE LOW AMPLITUDE NATURE OF THE UPPER PATTERN.

ON DAY 4/MONDAY...AS A SHORTWAVE TROUGH POTENTIALLY SPREADS EASTWARD OVER THE NORTHERN ROCKIES AND MOISTURE BEGINS TO RETURN ACROSS THE SOUTH-CENTRAL CONUS...CURRENT THINKING IS THAT ELEVATED TSTMS...PERHAPS SOME SEVERE WITH HAIL...WILL INCREASE MONDAY NIGHT/EARLY TUESDAY ACROSS PORTIONS OF THE MIDWEST AND MIDDLE/UPPER MS VALLEY.

BY DAY 5/TUESDAY...THE AFOREMENTIONED SHORTWAVE TROUGH IS EXPECTED TO CROSS THE NORTHERN PLAINS/UPPER MIDWEST. SEVERE TSTMS SEEM PROBABLE TUESDAY AFTERNOON/NIGHT ACROSS PORTIONS OF THIS MIDWEST/MISSISSIPPI VALLEY TO UPPER GREAT LAKES REGION...ESPECIALLY INCLUDING PORTIONS OF MO/IL. HOWEVER...MODEST NUMERICAL GUIDANCE VARIABILITY REGARDING THE UPPER MIDWEST SHORTWAVE TROUGH...COUPLED WITH SOME CONCERN FOR A STRONG ELEVATED MIXED LAYER/CAP ACROSS THE WARM SECTOR GIVEN THE PROGGED POSITION OF THE UPPER TROUGH...PRECLUDES THE AREAL DELINEATION OF A 30 PERCENT SEVERE RISK AREA AT THE CURRENT DAY 5 JUNCTURE.

BY DAY 6/WEDNESDAY...THE COLD FRONT SHOULD STALL IN A GENERAL NORTHEAST-SOUTHWEST ORIENTATION FROM THE OH VALLEY TO THE SOUTHERN PLAINS. AN ISOLATED SEVERE THREAT MAY EXIST ALONG THIS FRONTAL ZONE...WITH A SEVERE THREAT ALSO POSSIBLE ACROSS PORTIONS OF OK/NORTH TX NEAR A POSSIBLE SURFACE LOW/FRONT/DRYLINE TRIPLE POINT. BUT AGAIN...SPECIFIC PREDICTABILITY IS QUITE LIMITED BY THIS JUNCTURE AMID LOW AMPLITUDE SOUTHWESTERLY/CYCLONIC UPPER FLOW.

The NWS Chicago/Romeoville WSR-88D KLOT radar is in the initial stages of a catastrophic failure of the gearing in the radar pedestal. A five person team from the WSR-88D Radar Operations Center (ROC) will perform a rebuilding of the gears in the pedestal. This is a significant failure, and the reconstruction of the pedestal gears will require that the radar be out of service for 7 to 10 days. The condition was identified when other routine maintenance was being performed. Because the problem was discovered early, it is believed that the radar pedestal still has some operational service time left. In order to utilize and maximize this remaining service time, the radar will only be operated sparingly until the reconstruction begins. Operation of the system will be curtailed during quiet weather, and the radar placed into service when widespread or significant rain is within the coverage area. The radar will then be down through at least late next week while the reconstruction of the pedestal is being completed.

It's still several days out, but I don't think this timeframe is looking as good for my area as it did a day or two ago.

On Monday, there is going to be a lot of instability present in Oklahoma, but very poor wind shear, and a strong cap. We're going to need a trigger to break that cap, and as of right now, I don't see one...but if we do end up breaking the cap Monday, then I could see some pulse severe storms affecting Oklahoma.

Tuesday looks more like a squall line setup for Oklahoma.

The good news is it looks like we are entering an active period, with another system affecting the Southern Plains late next week.

IMO i do not see anything that just screams outbreak or anything but I am sure some severe weather will be possible with this system. I wish us here in Ohio could get into the action it's been rather uneventful in this neck of the woods so far, but its still early.

00z GFS leads me again to believe that nothing is going to happen here on Monday. Doubt the SPC even throws in a See Text down here; I just see no signs of anything being able to initiate.

Tuesday to me looks like a squall line threat down here, although I can already tell it's possible that, like with every other system that came through here over the last two months, the convection could fire just to the east. I definitely think there will be a fairly big wind damage threat here on Tuesday though, with more discrete storms possible further to the northeast closer to the low where surface winds are backed somewhat.

...DISCUSSION... PER 00Z ECMWF/GEFS/UKMET GUIDANCE...A RELATIVELY LOW AMPLITUDE/FAST MOVING BELT OF WEST-SOUTHWESTERLY MID-UPPER FLOW WILL PREVAIL THROUGH THE MIDDLE/LATE PART OF THE UPCOMING WEEK. OWING TO THE LOW AMPLITUDE NATURE OF THE UPPER PATTERN...A MODEST PREDICTABILITY REGIME EXISTS ESPECIALLY BY DAYS 6-8.

FOR DAY 4/TUESDAY...ALTHOUGH A MODEST DEGREE OF LARGE SCALE VARIABILITY STILL EXISTS AMONGST AVAILABLE NUMERICAL GUIDANCE...A SHORTWAVE TROUGH IS EXPECTED TO CROSS THE MO VALLEY/UPPER MIDWEST ON TUESDAY. AHEAD OF AN ADVANCING SURFACE LOW/COLD FRONT...IT SEEMS LIKELY THAT A RELATIVELY MOIST AIRMASS /LOWER TO PERHAPS MIDDLE 60S F SURFACE DEWPOINTS/ WILL BE IN PLACE ACROSS THE REGION. AFTER THE POSSIBILITY OF SOME EARLY MORNING HAIL...SEVERE TSTMS ARE PROBABLE TUESDAY AFTERNOON/NIGHT ESPECIALLY ACROSS PORTIONS OF THE MIDWEST/OZARKS AND MIDDLE MISSISSIPPI/LOWER OH VALLEYS...PERHAPS CENTERED ACROSS PORTIONS OF IL/MO. GIVEN AMPLE LOW LEVEL MOISTURE/VERTICAL SHEAR...WELL-ORGANIZED SEVERE STORMS INCLUDING SUPERCELLS/BOWS SEEM LIKELY TUESDAY AFTERNOON/NIGHT...WITH ALL SEVERE HAZARDS POSSIBLE INCLUDING TORNADOES.

INTO DAY 5/WEDNESDAY...THE COLD FRONT SHOULD STALL IN A GENERAL NORTHEAST-SOUTHWEST ORIENTATION FROM THE OH VALLEY TO THE SOUTHERN PLAINS. AN ISOLATED SEVERE THREAT MAY EXIST ALONG THIS FRONTAL ZONE...WITH AT LEAST A CONDITIONAL-TYPE SEVERE THREAT ALSO POSSIBLE ACROSS PORTIONS OF OK/NORTH TX NEAR A POSSIBLE SURFACE LOW/FRONT/DRYLINE TRIPLE POINT. BUT GIVEN CURRENT EXPECTATIONS FOR MODEST LARGE SCALE FORCING...A SEVERE RISK AREA IS NOT CURRENTLY WARRANTED.

FOR DAYS 6/7 THURSDAY/FRIDAY...AVAILABLE 00Z BASED GUIDANCE IS GENERALLY INDICATIVE OF ANOTHER SHORTWAVE TROUGH CROSSING THE WESTERN/CENTRAL STATES. GIVEN THE ARRIVAL OF LARGE SCALE FORCING FOR ASCENT...IT IS PLAUSIBLE THAT A SEVERE TSTM THREAT WILL BE FOCUSED ESPECIALLY ON THE WEST EDGE OF THE MOIST AXIS POTENTIALLY INCLUDING PORTIONS OF THE SOUTHERN PLAINS/LOWER MO VALLEY TO MIDDLE MS VALLEY THURSDAY INTO FRIDAY.

LOW LEVEL MOISTURE TRANSPORT WILL INCREASE MONDAY NIGHT INTOTUESDAY UNDER STEEP MID-LEVEL LAPSE RATES COMING IN FROM THE WESTON STRONG ZONAL FLOW. DO NOT EXPECT MUCH MORE THAN ISOLATEDTHUNDERSTORMS ON MONDAY AS FORECAST SOUNDINGS ARE SHOWING ASUBSTANTIAL WARM LAYER BETWEEN 800-600MB. AS WE GO INTO MONDAYNIGHT THROUGH TUESDAY NIGHT...THUNDERSTORM CHANCES WILL INCREASEAS LARGE SCALE ASCENT INCREASES AHEAD OF A RATHER STRONG MID LEVELSHORTWAVE TROUGH. SET-UP WITH THE CONFLUENT TROUGH AND NORTHEAST-SOUTHWEST ORIENTED COLD FRONT IS SIMILAR TO WHAT WE HAVE SEEN ONTWO OCCASIONS EARLIER THIS MONTH...HOWEVER FORECAST MLCAPES FROMBOTH THE GFS/ECMWF ARE ON THE ORDER OF 2000 J/KG. GIVEN THESEVALUES...DECENT ASCENT AND 40-50KT DEEP LAYER SHEAR IT SEEMS THATWE ARE SETTING UP FOR ANOTHER ROUND OF SEVERE WEATHER DURING THISPERIOD. THIS SYSTEM MOVES QUICKLY EAST WHICH WILL LIKELY PROVIDEDRY DAYS WEDNESDAY AND THURSDAY...BUT GFS/ECMWF DO SHOW ANOTHERSTORM SYSTEM WHICH WILL LIKELY GIVE US ANOTHER ROUND OFTHUNDERSTORMS LATE IN THE WEEK.

TUES/TUES NIGHT STILL LOOK LIKE THE BEST SHOT AS ANOTHERAGGRESSIVE SYSTEM MAKES ITS WAY OUT OF THE CENTRAL PLAINS INTO THEMIDWEST. MODELS MAY BE A LITTLE OVERBLOWN WITH THE SFC SYSTEM ASIT MOVES ACROSS THE FA WITH A WIDE OPEN WAVE ALOFT AND SUCH A DEEP WRAPPEDUP SYSTEM AT THE SFC...HOWEVER...MODELS ARE HINTING AT A BIT OF ANEG TILT AS THE TROF MOVES INTO THE FA AND WILL HAVE TO BE WATCHEDCAREFULLY. FOR NOW...NO PROBLEMS WITH GOING LIKELY ON DAY 4.